Abstract
Photovoltaic restoration of sight requires intense near-infrared light to effectively stimulate retinal neurons. We assess the retinal safety of such radiation with and without the retinal implant. Retinal damage threshold was determined in pigmented rabbits exposed to 880nm laser radiation. The 50% probability (ED50) of retinal damage during 100s exposures with 1.2mm diameter beam occurred at 175mW, corresponding to a modeled temperature rise of 12.5°C. With the implant, the same temperature was reached at 78mW, close to the experimental ED50 of 71mW. In typical use conditions, the retinal temperature rise is not expected to exceed 0.43°C, well within the safety limits for chronic use.
Highlights
Electrical stimulation of the retina allows restoration of visual perception in patients blinded by retinal degeneration [1, 2]
Retinal damage was assessed by whitening of the retina under slit lamp examination (Fig. 1(A)), and by OCT (Fig. 1(B)-1(C))
Rabbits with subretinal implants required prompt measurements of the damage threshold since the avascular rabbit retina is affected by the separation from RPE within hours (Fig. 2)
Summary
Electrical stimulation of the retina allows restoration of visual perception in patients blinded by retinal degeneration [1, 2]. Photovoltaic arrays allow a completely wireless and modular design of the implant, thereby greatly simplifying the implantation procedure [3,4,5]. In this approach, photodiodes convert incoming light into electric current in each pixel. Previous studies demonstrated that NIR (880nm-915nm) light elicits retinal responses to photovoltaic stimulation with irradiance ranging from 0.1 to 5mW/mm, and pulse durations of 1 to 10ms [4, 5]
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